1. Field of the Invention
This invention relates to an exhaust system for an internal combustion engine with so called compression wave supercharger in which a compression wave energy of an exhaust gas is utilized for compressing an intake gas to get a supercharging effect of the intake gas, more specifically to an exhaust system in which an exhaust gas recirculation (hereinafter referred to as EGR) port for introducing EGR gas therefrom is provided.
2. Description of the Prior Art
An exhaust system with a compression wave supercharger is disclosed in for example, Japanese Patent Public Disclosure No. 61-31652, laid open to the public on Feb. 14, 1986, which corresponds to U.S. Pat. No. 4,702,218 wherein the exhaust system is provided with an EGR control system for reducing Nox in the exhaust gas.
The compression wave supercharger disclosed in the above Japanese publication is provided with a casing, a rotor rotatably mounted on the case, provided with a plurality of radially extending partitions to define a plurality of axially extending gas chambers. The casing is provided with opposite ends facing to the rotor wherein one of the end of the casing is formed with an inlet and outlet for the exhaust gas and the other end is formed with an inlet and outlet for the intake gas. The exhaust gas is introduced into the gas chambers of the rotor rotating to compress the intake gas by utilizing the exhaust gas energy for thereby obtaining a supercharging effect. The exhaust system disclosed in the Japanese publication is also provided with an EGR port to which an EGR passage is connected for introducing an EGR gas thereinto.
In such an exhaust system of the engine with the compression wave supercharger and the EGR control system, in utilizing energy of the exhaust gas, it is desirable on one hand to suppress a pulsation effect or dynamic effect of the compression wave of the exhaust gas introduced in the gas chambers of the rotor wherein the pulsation of the exhaust gas is produced because of, for example, the different operating phases of respective cylinders in a reciprocating engine and of rotors in a rotary piston engine so that a uniform supercharging effect can be obtained. On the other hand, it is desirable to take advantage of the pulsation effect of the compression wave so that the EGR gas can be effectively introduced into the EGR passage.
It should however be noted that the conventional exhaust systems of the engine with both the compression wave supercharger and the EGR control system is not sufficient in obtaining both a desirable supercharging effect and an efficient introduction of the EGR gas.